We have established the concept that carcinoma is a pathology of embryology. This research is to test the hypothesis that if one embryonic field can regulate its closely related carcinoma (as the blastocyst regulates embryonal carcinoma) then there should be an embryonic field capable of regulating each type of carcinoma. To this end the neural crest will be tested to see if it regulates tumor formation of neuroblastoma and melanoma. If regulation occurs, attempts will be made to make mice chimeric in neural crest-derived tissues by the injection of small numbers of neuroblastoma cells into mouse embryos of appropriate gestational ages. The injected embryos will be injected into the uteri of appropriate hosts and the offspring will be analyzed for chimerism using isoenzyme analyses and pigmentation. The cell types responsible for the inductions will be identified using the techniques successful in the studies of blastocyst control of tumor and colony formation of embryonal carcinoma. These studies will involve tissue culture, embryo dissection, microinjection of electron microscopy, etc. Then we will study the mechanism of the control. Is there a diffusible molecule or is it membrane-bound? Is metabolic cooperation required?